Fluorohydrocarbon substituted methylsiloxanes



Patented Oct. 16, 1951 UNITED STATES PATENT OFFICE FLUOROHYDROCARBONSUBSTITUTED METHYLSILOXANES ration of New York No Drawing. ApplicationOctober 2'7, 1949, Serial No. 123,992

6 Claims. (01. 260 4483) The present invention relates to a new class oforganosilanes and to methods for their preparation.

In general in the organosilicon art the organic radicals which arelinked to silicon are monovalent hydrocarbon radicals. U. S. Patent2,258,- 219 describes the preparation of chlorophenylsilicon chloridesand fluorophenylsilicon chlorides. The hydrolyzates of these silanes arereadily condensable similarly to silanes which do not contain halogensubstituents in the organic radicals.

I have shown that the hydrolysis of silanes in which all of thesubstituents are chlorine, trifiuorotolyl and hexafluoroxylyl producesstable silanols which are resistant to condensation to siloxanes. Thisresistance to condensation of the silanols appears to be due to thepresence on the silicon atoms of trifiuoromethyl substituted phenylradicals.

Objects of the present invention are to provide siloxanes, the siliconatoms of which carry trifluoromethyl substituted phenyl substituents onthe silicon atoms.

'Siloxanes in accordance herewith are of the general formula:

in which n is a positive integer less than 3 and a:

has an average value of from 3 to 10, inclusive.

The siloxanes hereof may be produced by any suitable method, as forexample, by the hydrolysis of the corresponding dichlorosilanes followedby the condensation of the hydrolysis product. The correspondingdichlorosilanes may be produced by any suitable method, as for example,the interaction of methyltrichlorosilane with a,Grignard reagentprepared by reacting a trifluoromethyl substituted bromobenzene withmagnesium at a temperature below 80 C. The

' Grignard reagent so produced is reacted with The coupling of theBromination 01. these compounds can also be obtained by passing amixture of the fluorohydrocarbon and bromine in vapor phase through areactor at a temperature in the range of '100 to 900 C. By this methodthe ortho compounds can be obtained as well as the meta compounds,together with small amounts of the para derivative.

One suitable compound for the preparation of the bromide istrifluoromethylbenzene. Other bromides may be prepared from thebis(trifluoromethyDbenzenes such as the compounds of this type in whichthe two trifluoromethyl radicals are in the 1,3 and 1,4 positions.

The Grignard reagents are produced by reacting the bromides as abovedescribed with magnesium. It should be noted that great care should beemployed in the preparation and handling of these Grignard reagentsinasmuch as violent explosions may occur, particularly it thetemperature limit herein stated is exceeded. In the reaction of thesebromides with the magnesium the temperature should be held below 80 C.It is also of assistance in preventing detonation of these materials tooperate in the presence of a solvent such as ether, or a low boilinghydrocarbon. The chlorine analogues of the above bromides do not appearto form Grignard reagents under the conditions stated.

The Grignard reagents so produced are then reacted withmethyltrichlorosilane. The methyltrichlorosilane is mixed with theGrignard reagent and maintained at below 80 C. The coupling reactionproceeds with relative ease.

' In making the coupling, the silicon chloride is employed in amount atleast equivalent to the amount of Grignard reagent employed. Preferablyless than ten equivalents of the silicon chloride are present perequivalent of the Grignard reagent.

The products of the coupling reaction are of the type:

SiCl:

(C In). H3

rials may be of utility as plasticizers for fluoro carbon polymers.

The present invention is a continuation in part of my application,Serial Number 786,541, filed\ November 17, 1947.

The following examples illustratethe present invention:

Example 1 Trifluoromethylphenyl bromide was reacted with an equivalentamount of metallicmagnesium in the presence of 500 cc. of diethyl etherper 225 grams oi the bromide. The Grignard reagent so produced wasreacted with methylsilicon triehloride in the amount of one mol of theGrignard reagent per two mols of the silicon chloride. The magnesiumhalide salt which was precipitated was separated from the etherealsolution.

The solution was distilled, and the following products were recovered:

B. P., C. D2si4 1m" (ll FRCFIFHCFifliCh. I 115.5 8.1; 50 mm- 1. 3436 1.4639 (2) (F3CC6H02CH3SiCl 123 8t 4 111111;.-- 1. 3535 1. 4841 Compound(1) was a low viscosity fluid. This chloride was dissolved in diethylether. Water in excess was added to the ethereal solution.

The hydrolyzate was a low viscosity oil of 100 centistokes at roomtemperature which did not crystallize. While polymeric dimethyl siliconeforms a,gel when exposed to air at 250 C., for

eighteen'hours, the hydrolyzate of compound 1) did not become soliduntil it had been held for ilve hundred hours under these conditions.Even following properties:

1m: c. DWI" Sp. Rei.

Cntl 1.4698 1.318 0.2111 Cut 2 1. 4101 1. 319 0.2116 Residue 1. 4739 1.339 0. 2099 Cuts 1 and 2 are cyclic siloxanes of the formula abovestated, in which the cyclic structure is cyclic trisiloxane and cyclictetrasiloxane. The residue contained cyclic'siloxanes of the formulaindicated. in which the valueoi a: is equal to as i h as 10.

Example 2 Compounds 01' the formula:

where a: has a value of from 3 to 10, inclusive.

At a temperature of 0., butyl chloride in amount of 372 grams was addedto 75 grams of metallic lithium in the form or shot suspended in oneliter of ether. An atmosphere of helium was maintained in the reactionvessel during the was produced.

The lithium derivative produced as above described was added to grammols of methyltrichlorosilane at between --10 and 0 C. The reactionmixture was then heated to cause refluxing of the ether. The product wasfiltered to remove the salt and strip distilled to remove the ether.Residue of 990 grams of product was obtained. This product wasfractionally distilled in a Podbielniak still. Upon distillation twoplateaus were observed, one at 983 C. at a pressure of 25.5 mm. ofmercury, and the other at 100.7 C. at 24 mm. of mercury. Each oi theseplateaus includes various isomers. However, both plateaus wererelatively pure mixtures of isomers having the formula:

on), HIV These two cuts were next dissolved in benzene and hydrolyzed byshaking with the amount of water theoretically necessary to eflecthydrolysis of the silicon bonded chlorine. The hydrolysis product waswashed with additional water and finally with dilute sodium bicarbonatesolution. The product was again washed with water and enough benzene wasadded to make the product" layer of lower specific gravity than water.This solution of product in benzene was refluxed inmixture with waterfor four hours. The benzene solution of product was then dried incontact with sodium sulphate. The benzene was strip distilled from theproduct and the product then distilled under vacuum. By distillation at.4 mm. mercury, symmetrical trimethyl tris(hexafiuoroxylyl)cyclotrisiloxane was obtained which had a boiling point of 169 C. at thepressure employed; This material had the properties: nzsof 1.4380; D of1.483; and a specific refraction of 0.1770. Higher cyclicmethyl(hexafluoroxylyl) polysiloxanes were obtained as a residue whichcyclic siloxanes contained materials having up to about 10 polymer unitsper cycle. This residue was a highly viscous water white fluid.

The specific reiractions referred to above may be compared withtheoretical bond refractions computed in accordance with the methoddescribed by E. L. Warrick. Journal oi the American Chemical Society,volume 68 (1946), page 2455.

That which is claimed is:

[ -sl1o- (CFI): 41K:

in which n is a positive integer less than 3 and a: has an average valueof from 3 to 10 inclusive.

in which a: has anaverage value of from 3 to 10 inclusive. I

. 5 6 8. 6. Symmetrical trimethyltrismexafluoroxylyl) Icyclotrisiloxane. I: 10-1 CHARLES F. KOHL, JR.

(CFa): H: V REFERENCE ITED in which a: has an average value of from 3 to10 5 s c inclusive The following references are of record in the file ofthis patent:

UNITED STATES PATENTS I: l m Number Name Date 1%) 4 2,258,219 RochowOct. 7, 1941 5 2,258,222 Rochow Oct. 7, 1941 cm it l 1 15

